Fuel pump turbulence 8BA

F

Fairlane514

Senior Member
8BA with sediment bowl and mechanical fuel pump.

I noticed when running, there is turbulence in the sediment bowl. Seems like that's not right.

Also had to prime carburetor to get it to start only after about 4-5 days.

Rebuilt Holley 94, runs fine after priming.

Not sure how old the pump is, looks pretty clean from the outside, but may need a diaphragm.
 
May have an inlet check valve not quite sealing in that pump. That might push some fuel back with each stroke and disturb the bowl as well as making it "lose prime".
 
Ok, thanks

Been trying to find an Apco kit, to no avail.

I have the part number 11A-9349, it pops up, but not stating Apco.

I want to use a quality kit obviously.
 
Thirdgen.com or vanpeltsales.com may have an ethanol resistant kit……could what you call “turbulence “ be an air leak at the fuel bowl?…….Mark
 
Air leak would equal fuel leaking. Rebuilding the pump with ethanol resistant kit is a good thing to do however, it will not affect the way ethanol reacts to heat. The alcohol level in ethanol lowers its bowling point.

If you have doubts, try cooling the fuel bowl when the turbulence occurs.
 
I ordered a kit and some extra sediment bowl gaskets. Hopefully this will cure it.

I do have a metal cased fuel filter before the pump, secured with worm style hose clamps.
 
Is your metal fuel filter away from where it can get warm?……a lot of issues with ethanol blended fuel are caused by heat. The cooler you can keep the fuel, the less problems you may have, IMO……….Mark
 
FlatTopFreddie said:
Air leak would equal fuel leaking. Rebuilding the pump with ethanol resistant kit is a good thing to do however, it will not affect the way ethanol reacts to heat. The alcohol level in ethanol lowers its bowling point.

If you have doubts, try cooling the fuel bowl when the turbulence occurs.
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No way would it leak fuel.
Also, not an indication of the so-called vapor lock.
 
FlatTopFreddie said:
So which side of the pump is vacuum? (Tank side) Isnt the fuel bowl side pressurized? Air on that side would cause a fuel delivery problem.
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I have always wondered about this! Air or vapor on the suction side would definitely stop fuel delivery. But wouldn’t a bubble of vapor on the pressurized side just get pushed along into the carb where it would escape out the carb’s air vent? Wouldn’t the pump’s check valve keep a vapor bubble from backing up?
 
JayChicago said:
I have always wondered about this! Air or vapor on the suction side would definitely stop fuel delivery. But wouldn’t a bubble of vapor on the pressurized side just get pushed along into the carb where it would escape out the carb’s air vent? Wouldn’t the pump’s check valve keep a vapor bubble from backing up?
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Air bubbles or gas fumes are compressible (compare to a spongy brake pedal), while liquid fuel being pumped through the system is not compressible.
This sponginess translates to a reluctance of a fuel pump’s check valves to function as designed, often described as vapor lock, more correctly as loss of prime. A volume of vapor within the pump that exceeds the quantity of fuel to be moved in a single stroke will expand/contract, preventing fuel movement. This condition is self perpetuating, as the stagnant fuel gets hotter, creating more vapor and less movement of fuel.
 
I know you all think I’m nuts and not very credible… sorry you feel that way…

My experience is from years of driving Model A’s on tours around the country. Remember they are a gravity fed system. When ambient temperature is 70’s to upper 80’s all is well, no problem. But when ambient gets above 90, things change. Ethanol will boil in the fuel bowl. Looks like a little water spout inside the bowl. Along with comes vaporization in the top of the bowl. Typically happens when slowing down from cruising speed to traffic conditions.

Same car and same weather conditions, Non-Ethanol, no boiling, turbulence or vaporization.

It also occurs with my other drivers, 36 Ford, 47 Mercury and 54 Chevrolet.

The only successful remedy we have found is cooling the fuel bowl.

If Non-Ethanol is available to you, give it your own test…

I’m sure most of you can remember when gasoline was not ethanol … this problem didn’t exist.
 
FlatTopFreddie said:
I know you all think I’m nuts and not very credible… sorry you feel that way…

My experience is from years of driving Model A’s on tours around the country. Remember they are a gravity fed system. When ambient temperature is 70’s to upper 80’s all is well, no problem. But when ambient gets above 90, things change. Ethanol will boil in the fuel bowl. Looks like a little water spout inside the bowl. Along with comes vaporization in the top of the bowl. Typically happens when slowing down from cruising speed to traffic conditions.

Same car and same weather conditions, Non-Ethanol, no boiling, turbulence or vaporization.

It also occurs with my other drivers, 36 Ford, 47 Mercury and 54 Chevrolet.

The only successful remedy we have found is cooling the fuel bowl.

If Non-Ethanol is available to you, give it your own test…

I’m sure most of you can remember when gasoline was not ethanol … this problem didn’t exist.
Click to expand...

Freddie, you’re not nuts and many if not most of us have experienced similar problems. But then there are those who haven’t had any of those things happen to them and blame it all on poor maintenance. It’s curious that those are the same folks whose grandmothers believed in keeping a ladleful of water handy at the well pump in case she had to prime the pump to get water in the morning.
 
Finally got my rebuild kit installed on the pump. My old sediment bowl gasket was rubber and cracked, but stuck pretty good the the housing.
My kit came with the cork one.

The original rubber flex line from the pump was not present, so I installed one.

Question.......is the female end 7/16x24? It appears to be an inverted flare, so I am planning on 1/4 brake line over and down to my filter and main line back to the tank. Main line is 1/4 inch copper.
 
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